DBG handlers.
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Authored by kib on Dec 25 2020, 10:04 PM.

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rGd39f7430a6e1: amd64: preserve %cr2 in NMI/MCE/DBG handlers.

Summary

These handlers could interrupt code which has interrupts disabled, and if a spurious page fault occurs during exception handler run, we get clobbered %cr2 in higher level stack.

This is mostly a speculation, but it is based on hints from good sources.

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rG FreeBSD src repository

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Event Timeline

kib requested review of this revision.Dec 25 2020, 10:04 PM

kib created this revision.

markj accepted this revision.Dec 27 2020, 3:30 AM

markj added inline comments.

sys/amd64/amd64/exception.S
943	BTW, I think this comment should say %ebx != 0 => return to userland. Same in the mchk handler. Assuming this is correct I'll fix it after this diff is pushed, or feel free to do it yourself.

This revision is now accepted and ready to land.Dec 27 2020, 3:30 AM

Closed by commit rGd39f7430a6e1: amd64: preserve %cr2 in NMI/MCE/DBG handlers. (authored by kib). · Explain WhyDec 27 2020, 11:16 AM

This revision was automatically updated to reflect the committed changes.

kib added a commit: rGd39f7430a6e1: amd64: preserve %cr2 in NMI/MCE/DBG handlers..